/Engine/Source/Editor/UnrealEd/Public/Subsystems/EditorAssetSubsystem.h
Broadcasting this will also call anything added with AddOnExtractAssetFromFile.
[FOnExtractAssetFromFile](API\Editor\UnrealEd\Subsystems\UEditorAssetSubsystem\FOnExtractAssetFromFile) & GetOnExtractAssetFromFile()